linux-kernel - Re: [PATCH v3 1/1] mtd: nand: pxa3xx: Set FORCE

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Date:   Sun, 15 Oct 2017 20:55:43 +0000
From:   Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To:     Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Kalyan Kinthada <Kalyan.Kinthada@...iedtelesis.co.nz>
CC:     "dwmw2@...radead.org" <dwmw2@...radead.org>,
        "computersforpeace@...il.com" <computersforpeace@...il.com>,
        "marek.vasut@...il.com" <marek.vasut@...il.com>,
        "richard@....at" <richard@....at>,
        "cyrille.pitchen@...ev4u.fr" <cyrille.pitchen@...ev4u.fr>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "ezequiel.garcia@...e-electrons.com" 
        <ezequiel.garcia@...e-electrons.com>,
        "miquel.raynal@...e-electrons.com" <miquel.raynal@...e-electrons.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/1] mtd: nand: pxa3xx: Set FORCE_CSX bit to ARMADA370
 variants.

Hi Boris,

On 15/10/17 02:13, Boris Brezillon wrote:
> Hi Kalyan,
> 
> On Thu, 28 Sep 2017 13:57:56 +1300
> Kalyan Kinthada <kalyan.kinthada@...iedtelesis.co.nz> wrote:
> 
>> When the arbitration between NOR and NAND flash is enabled
>> the <FORCE_CSX> field bit[21] in the Data Flash Control Register
>> needs to be set to 1 according to guidleine GL-5830741 mentioned
>> in Marvell Errata document MV-S501377-00, Rev. D.
> 
> The real question is, is this patch fixing a real bug or are you just
> setting this bit because a guideline says it should be set?

Yes that's a fair summary. It is in a document called "Functional 
Errata" so there is some feeling here that we (allied telesis) should 
follow up things in these kinds of documents.

> As far as I
> understand, noone fully understands what this bit does and why it needs
> to be set, so if you're not fixing a real bug, I'd prefer keeping the
> code unchanged code until someone complains for a good reason.

Agreed. We've certainly not noticed a change in behaviour on our boards. 
I've requested more information from Marvell through their support 
channels. I'll share what I can if/when they come back with something 
useful.

> 
> Regards,
> 
> Boris
> 
>>
>> This commit sets the FORCE_CSX bit to 1 for all
>> ARMADA370 variants as the arbitration is always enabled by default.
>> This change does not apply for pxa3xx variants because the FORCE_CSX
>> bit does not exist/reserved on the NFCv1.
>>
>> The NDCR_ND_MODE conflicts with the new NDCR_FORCE_CSX but is unused so
>> remove it along with NDCR_NAND_MODE.
>>
>> Signed-off-by: Kalyan Kinthada <kalyan.kinthada@...iedtelesis.co.nz>
>> ---
>>   drivers/mtd/nand/pxa3xx_nand.c | 9 +++++++--
>>   1 file changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/mtd/nand/pxa3xx_nand.c b/drivers/mtd/nand/pxa3xx_nand.c
>> index 85cff68643e0..a6a7a5af7bed 100644
>> --- a/drivers/mtd/nand/pxa3xx_nand.c
>> +++ b/drivers/mtd/nand/pxa3xx_nand.c
>> @@ -67,8 +67,7 @@
>>   #define NDCR_DWIDTH_M		(0x1 << 26)
>>   #define NDCR_PAGE_SZ		(0x1 << 24)
>>   #define NDCR_NCSX		(0x1 << 23)
>> -#define NDCR_ND_MODE		(0x3 << 21)
>> -#define NDCR_NAND_MODE   	(0x0)
>> +#define NDCR_FORCE_CSX		(0x1 << 21)
>>   #define NDCR_CLR_PG_CNT		(0x1 << 20)
>>   #define NFCV1_NDCR_ARB_CNTL	(0x1 << 19)
>>   #define NFCV2_NDCR_STOP_ON_UNCOR	(0x1 << 19)
>> @@ -1464,6 +1463,9 @@ static int pxa3xx_nand_config_ident(struct pxa3xx_nand_info *info)
>>   	info->chunk_size = PAGE_CHUNK_SIZE;
>>   	info->reg_ndcr = 0x0; /* enable all interrupts */
>>   	info->reg_ndcr |= (pdata->enable_arbiter) ? NDCR_ND_ARB_EN : 0;
>> +	/* Set FORCE_CSX bit for all ARMADA370 Variants. Ref#: GL-5830741 */
>> +	if (info->variant == PXA3XX_NAND_VARIANT_ARMADA370)
>> +		info->reg_ndcr |= NDCR_FORCE_CSX;
>>   	info->reg_ndcr |= NDCR_RD_ID_CNT(READ_ID_BYTES);
>>   	info->reg_ndcr |= NDCR_SPARE_EN;
>>   
>> @@ -1498,6 +1500,9 @@ static void pxa3xx_nand_detect_config(struct pxa3xx_nand_info *info)
>>   	info->reg_ndcr = ndcr &
>>   		~(NDCR_INT_MASK | NDCR_ND_ARB_EN | NFCV1_NDCR_ARB_CNTL);
>>   	info->reg_ndcr |= (pdata->enable_arbiter) ? NDCR_ND_ARB_EN : 0;
>> +	/* Set FORCE_CSX bit for all ARMADA370 Variants. Ref#: GL-5830741 */
>> +	if (info->variant == PXA3XX_NAND_VARIANT_ARMADA370)
>> +		info->reg_ndcr |= NDCR_FORCE_CSX;
>>   	info->ndtr0cs0 = nand_readl(info, NDTR0CS0);
>>   	info->ndtr1cs0 = nand_readl(info, NDTR1CS0);
>>   }
> 
>